Start work on highlighting search results for nijel/weblate#42

So far this only knows about source strings.
Also highlight search results in context field (#42)
Capitalization fixes for search term highlight (#42)

Not profiled in any way. Hopefully not as bad as using `re.findall` to
spot variations and then using `str.replace`.
Fix some typos in documentation
Merge pull request #267 from ChrisOelmueller/typos

Fix some typos in documentation
Translated using Weblate (German)

Currently translated at 64.8% (517 of 798)
Translated using Weblate (Hebrew)

Currently translated at 73.4% (586 of 798)
Merge remote-tracking branch 'origin/master'
Catch only single exception
Improve git repository setup

With configured origin remote in global git config, current approach
failed as it had half existing remote (repo.remotes.origin did not
exist, but git remote did show it).

Now we do not try to add origin if git already sees it and we configure
branches to fetch, this should also prevent fetching of branches we
don't follow.

Fixes #268.
Another word to check
Fix logic of running consistency checks
Missing space
Wrap long line
Disable pylint warning on conditional import
Change string used for plurals separation

Using \x00 proven to be bad idea as some databases (eg. SQLite) does not
cope with string containing this. Using \x1e (Record Separator) should
be safe in this regard.

Fixes #266.
assing url contact value to contact_url
Merge pull request #270 from ruleant/contact_link

assing url 'contact' value to contact_url
Merge pull request #269 from ChrisOelmueller/highlight-search-results

Highlight search results
Changelog entry