First step in two-part process to rename directories to kallithea.
This first step is to change all references in the files where they refer
to the old directory name.

Imported some of the GPLv3'd changes from RhodeCode v2.2.5.

This imports changes between changesets 21af6c4eab3d and 6177597791c2 in
RhodeCode's original repository, including only changes to Python files and HTML.

RhodeCode clearly licensed its changes to these files under GPLv3
in their /LICENSE file, which states the following:
The Python code and integrated HTML are licensed under the GPLv3 license.

(See:
https://code.rhodecode.com/rhodecode/files/v2.2.5/LICENSE
or
http://web.archive.org/web/20140512193334/https://code.rhodecode.com/rhodecode/files/f3b123159901f15426d18e3dc395e8369f70ebe0/LICENSE
for an online copy of that LICENSE file)

Conservancy reviewed these changes and confirmed that they can be licensed as
a whole to the Kallithea project under GPLv3-only.

While some of the contents committed herein are clearly licensed
GPLv3-or-later, on the whole we must assume the are GPLv3-only, since the
statement above from RhodeCode indicates that they intend GPLv3-only as their
license, per GPLv3§14 and other relevant sections of GPLv3.

Added more detailed (and localized) information if hgsubversion is not
installed while enabling from settings

Added pre-create user hook.
It allows to control user creation using rcext hooks.

fixes issue #860.

IMC web commits poisoned caches when they failed. We now
always invalidate caches so objects are refreshed and will be accessible.

Implemented simple gist functionality ref #530.

- creation of public/private gists with given lifetime
- rhodecode-gist CLI for quick gist creation

UserGroup on UserGroup permissions implementation.
- user group can have another usergroup assigned
- it's impossible to assign usergroup on the same usergroup

recursive forks detach
- added API attrs for option to delete or detach forks
- deleting repos with attached forks raises an special Exception

configurable locking codes.
- this allows changing the default 423 LOCKED code to 2XX codes which don't break the transactions. Insted
it gives users a warning for push.

further cleanup of UsersGroup

Renaming some names ... but trying not to change API or database scheme.

Implemented basic locking functionality.

- Reimplemented how githooks behave
- emaulate pre-receive hook
- install missing git hooks if they aren't already in repo

Forbid changing changset status when it is associated with a closed pull request
- fixed some issues with cascade deleting repos with changeset statuses attached

fixed #72 show warning on removal when user still is owner of existing repositories
cleaned up exceptions

Added settings model, and Exceptions lib.
Filled settings with ldap settings.
Extended user db models with is_ldap flag, and added easier construction of RhodeCode db settings