cleanup: get rid of most "import *"

Apply script generated with the following hack:
(
hg loc '*.py'|xargs pyflakes-2 | sed -rn "s/([^:]*):.*'(.*)' may be undefined, or defined from star imports.*/sed -ri 's,\\\\<\2\\\\>([^=]|$),XXXX.\2\\\\1,g' \1/gp" | sort -u
hg loc '*.py'|xargs pyflakes-2 | sed -rn "s/([^:]*):.* undefined name '(.*)'$/sed -ri 's,\\\\<\2\\\\>([^=]|$),XXXX.\2\\\\1,g' \1/gp" | sort -u
hg loc '*.py'|xargs pyflakes-2 | sed -rn "s/([^:]*):.*'(from .*)\.([^.]*) import \*' used.*/sed -ri 's,\\\\<XXXX\\\\.,\3.,g' \1/gp" | sort -u
hg loc '*.py'|xargs pyflakes-2 | sed -rn "s/([^:]*):.*'(from .*)\.([^.]*) import \*' used.*/sed -ri 's,\2\\\\.\3 .*,\2 import \3,g' \1/gp" | sort -u
) | grep -v kallithea/bin/kallithea_cli_ishell.py > fix2.sh

diff: use fontello icon-diff-* names in generated html

This way we need less style code ... but generate slightly bigger html.

Also move the style code to kallithea-diff.less and remove the now obsolete
comment.

templates: change .node elements to <span>

This way we don't need to make them 'float: left'

codingstyle: trivial whitespace fixes

Reported by flake8.

pullrequests: rename "as_form" to something more descriptive

This parameter is (only) used for showing the PR contents preview on the
"New Pull Request" page.

tests: add as little code as possible in __init__.py

kallithea/tests/__init__.py contained quite a lot of code, including the test
base class TestController. This in itself may be considered bad practice.

Specifically, this poses a problem when using pytest 3.0+, in which asserts
in some files are not automatically rewritten to give improved assert
output. That problem can be fixed by explicitly registering such files for
assertion rewriting, but that register call should be executed _before_ said
files are imported. I.e. if the register call is in
kallithea/tests/__init__.py, assert calls in __init__.py itself can not be
rewritten.

Since the TestController base class does effectively contain asserts, and we
do not want to execute the register call from somewhere outside the
kallithea/tests directory, we need to move the TestController class to
another file (kallithea/tests/base.py) so we can have a register call in
__init__.py before loading base.py.

While not strictly necessary to fix the mentioned pytest problem, we take
the opportunity to fully clean __init__.py and move everything to
the new kallithea/tests/base.py. While doing so, unnecessary imports are
removed, and imports are ordered alphabetically. Explicit imports of symbols
from modules that were already imported as a whole, are removed in favor of
fully qualifying the references (e.g. tempfile._RandomNameSequence).

diff: minor cleanups

More consistency and preparing for later changes.

pullrequests: use monospace for hashes - columns of hashes look messy when they have different lenght

17f9f921a538 was insufficient.

pytest migration: rename TestControllerPytest back to TestController

The name TestControllerPytest was introduced to allow a temporary situation
where nose/unittest and pytest-based tests could coexist.
This situation is now over, so the base test class can be renamed again.

pytest migration: convert simple functional tests to TestControllerPytest

Replace usage of TestController with TestControllerPytest for those files in
tests/functional where there is no setUp/tearDown method (the pytest
equivalent to be investigated) and that do not use test parametrization.

pull requests: fix same git repository pull-request issue

Currentry, Kallithea can not create pull-request from same git repository.
Because, ancestor variable is not initialized when create pull-request from same git repository.

This patch find ancestor by `git merge-base` command and initialize it.

Second step in two-part process to rename directories.
This is the actual directory rename.