Implement simple string substitution for templates and javascript code.

We still have to provide for the index.html, the .xml files, and I
haven't resolved why the Hive view is failing to show the substitution.
Include the simple string substitution function s() in the headers of
view files that don't yet use it.
Track down some missed string customizations.

There's still one in the initial menusheet view, if visited without any
login.

There's also still index.html, but I have a good idea for that.
Include some guidance in customAppStrings.json.
Include index.html among the brand-customizable files with an entry in
elements.json, and include (AcmeSync) examples of index.html and
customAppStrings.json in custom/brand_examples.

All that remains to be accounted for, that I know about, is the manifest
.xml file.
Confirm the essential customizeString functionality with tests.
Merge branch 'master' of https://github.com/SpiderOak/SpiderOakMobileClient into issue-315-text-substitutions
Better way to handle index.html
Set Titles after settings are loaded
Allow branding the hive icon using the Strings
Merge pull request #317 from SpiderOak/issue-315-text-substitutions

Good improvement on index.html, and thanks for merging from master - sorry I missed that.