WIP: First attempt at chapter/verse trimming

Modifying (or subclassing) the UsxHelper class won't actually work,
since we're trying to store the *unmodified* (except for trimming)
USX in the database, not the HTMLified version. Still, the approach
is promising and some of this code can be reused, so it's worth saving.
WIP: Second attempt at chapter/verse trimming

This approach should work. There are still some bugs to be ironed
out, but it's reached a point that's worth saving.
WIP: USX trimmer seems to be working now

The USX trimmer class seems to be working properly now. Time to commit.
WIP: Demo of how to use UsxTrimHelper class
WIP: Special case for starting from front of USX

If user leaves start chapter & verse blank (wants to start from
beginnig of pasted/uploaded USX), then start by keeping, rather
than dropping, all start text (including any front matter).
WIP: Trimming now hooked up to new text dialog

UI still looks ugly -- some CSS work needed -- but it works, at least
for the single test I've run so far. More testing needed, and the UI
needs to be hooked up to the "edit existing text" dialog as well as
the new text dialog.
Remove a few debugging statements
Fix two bugs in UsxTrimHelper

* "Chapter #" was being duplicated for second & subsequent chapters
* Drop/keep checks were wrong for multi-chapter selections
WIP: Add some basic controls for ch/vs selection

These are ugly and need quite a bit of CSS tweaking, but they work.
Hook up controls on "Update Text" form
Make reset links functional
Use proper whitespace in HTML of UI elements
Improve CSS for chapter/verse selection forms
fixed "an user" typo
Fix missing close tag in sample USX
Merge branch 'master' into feature/chapterverseselection

Conflicts:
	src/angular-app/sfchecks/partials/questions-settings.html
Add unit tests for UsxTrimHelper class

Also fixed a minor bug revealed by the unit tests: an extraneous
</verse> closing tag (with no corresponding opening tag) was being
added to the end of the trimmed USX.
changed text on front page middle column to be even with left and right column

Added Read More button which displays a learn_how_it_works page with the full text
Merge branch 'feature/chapterverseselection'
Hide audio controls when audio is not available.