Configuration strip_xxx flags

Introduces strip_{note,template}_{braces,brackets,parens} and
strip_note_cloze to the configuration list. These new fields will be
usable within the add-on for controlling whether or not text gets
stripped out from various places.

These will be helpful for users who use cloze or stick things into their
input fields like "{familiar}", "[formal]", or "(Spain)".
Shorten tabs on Configuration screen

Provides additional space to accommodate the upcoming "Text" tab that
will handle taking the user's preferences for stripping and cloze
handling.
Add new options to configuration window

This introduces support for the configuration window to save and restore
combo boxes, with this being the first time for something like this.
Extend cloze options to on-the-fly

It turns out that Anki will render these using a special span tag in the
markup, so we actually will be able to identify and substitute these.
Notes about text handling on browser generator

Adds a reference to the new text-related configuration options on the
browser generator window.
Stripping brackets/parentheses/braces

Implements the changes to the main transformation lambdas in order to
check the configuration and apply the strip if the user has asked for
it.
Pass raw HTML from Reviewer through to lambdas

This is necessary now because the lambdas will be inspecting on-the-fly
output for <span class="cloze"></span> tags as the definitive marker of
such placeholders.
Cloze placeholder substitution

Introduces support for the cloze-related configuration settings,
allowing the user to intelligently swap out cloze placeholders with
either their hint, ellipses, or nothing at all.
Improved configuration messaging for cloze

Rephrases the labels and options so that they're hopefully a bit clearer
in what the substitution options do.
Make template helper cloze-aware

This adds a "Xxx uses cloze" checkbox when the user goes into a cloze
note and selects a field to insert into their template. If the user
selects to customize the inserted tag, then a reminder is printed
instead.
Collapse adjacent ellipses

It turns out that this is a handy thing to do: it avoids very long
pauses because of adjacent clozes, and it also helps from there being
too many periods when clozes appear at the end of sentences and the
like.
Merge branch 'add/strip-15-reattempt' into develop

Adds a myriad of options for handling and stripping text encountered by
the add-on, both in "from note" mode (e.g. mass generation) and "from
template" mode (e.g. on-the-fly).

Options include stripping parenthetical/bracketed/braced text and
different ways to deal with cloze deletion templates.

Fixes #15.