scripts: handle running with pending deleted files

Don't fail on files in manifest missing in working directory.

templates: rename email_templates to email

The '_templates' suffix is not really needed as we are already in a
'templates' dir.

This is more in line with the other templates, and the new 'ini' template
directory.

scripts: properly check for errors in whitespacecleanup/run-all-cleanup

An error in whitespacecleanup, like a bug in isort that raises an exception,
should be treated as a problem instead of silently ignored.

scripts: make output from run-all-cleanup easier to parse

Make it clear that it didn't end prematurely due to some invisible problem.

scripts: drop isort --wrap-length 160 - it is broken with py3 and not really necessary

Under Python 3, isort 4.3.21 failed with
https://github.com/timothycrosley/isort/issues/741 on
kallithea/controllers/api/api.py :

Traceback (most recent call last):
File "data/env/bin/isort", line 10, in <module>
sys.exit(main())
File ".../env/lib64/python3.7/site-packages/isort/main.py", line 379, in main
for sort_attempt in attempt_iterator:
File ".../env/lib64/python3.7/site-packages/isort/main.py", line 377, in <genexpr>
attempt_iterator = (sort_imports(file_name, **arguments) for file_name in file_names)
File ".../env/lib64/python3.7/site-packages/isort/main.py", line 88, in sort_imports
result = SortImports(file_name, **arguments)
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 207, in __init__
self._add_formatted_imports()
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 606, in _add_formatted_imports
self._add_from_imports(from_modules, section, section_output, sort_ignore_case)
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 526, in _add_from_imports
import_statement = self._multi_line_reformat(import_start, from_import_section, comments)
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 552, in _multi_line_reformat
dynamic_indent, indent, line_length, comments)
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 705, in _output_grid
if len(next_statement.split(self.line_separator)[-1]) + 1 > line_length:
TypeError: '>' not supported between instances of 'int' and 'str'

vcs: drop unused lockfiles.py

It popped up when investigating other things - make sure we don't waste more time on it.

front-end: Use DataTables from node_modules and stop bundling it

There is no minimized version in the npm package. For now, we just use the raw
one. We can minimize later.

front-end: Use select2 from node_modules and stop bundling it

select2 3.5.4 was added in 304e83e9bcde ... but the latest npm release in the 3
series is 3.5.1, so we use that one instead. We should probably upgrade to the
4 series.

The select2 images were not in the location the generated css pointed - now we
copy them from node_modules to the right location, next to the generated css.

Note: this will drop 190cb30841de "branches: fix performance of branch
selectors with many branches - only show the first 200 results" ... but it
should no longer be relevant now when we use server side filtering.

15e507047bae introduced select2-bootstrap.css - it is not clear what version
was used, but we use the latest 1.4.6 which also is very old.

front-end: Use jQuery and Flot from node_modules and stop bundling them

jquery.min.js 1.12.3 was introduced in 7a4dec17e837.

jquery.flot.js 0.8.3 was introduced in 322ce5147fe0.

js: introduce jquery.flot library - so far unused

Will be used to replace YUI flot.

Source files copied from https://github.com/flot/flot/tree/v0.8.3 .

mails: restructure notification mail content

* Mention "The Thing" in the header, link to online version
* Show The Thing
* A dense summary of the essentials of the context below it

The html indentation is odd in order to make the next diff smaller.

The text version is based on:

for a in kallithea/templates/email_templates/*.html; do sed -e 's,<\([^%/>]\|/[^%>]\)*>,,g' -e 's,\.html",\.txt",g' -e 's,^ *,,g' -e 's/}/|n,unicode}/g' $a > ${a%%.html}.txt ; done

whitespacecleanup: exclude email test reference

kallithea/tests/models/test_dump_html_mails.ref.html is expected to
contain trailing whitespace in the "-- " de-facto standard signature
separator (as e.g. referenced in RFC 3676, section 4.3).