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`.
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
No verbose logging in Jenkins