Smooth over some cross-browser CSP differences.

* Adding "foo.com" to your CSP via browser-policy now adds both
  "http://foo.com" and "https://foo.com". This smooths over the fact
  that some browsers interpret "foo.com" as "http://foo.com" and some
  interpret it as http AND https.
* Trim trailing slashes from origins. Firefox does not allow content
  from foo.com if you add "foo.com/" to your CSP.
Add frame-src to browser-policy-content.
Use regex to replace trailing slashes from browser-policy URLs.

Thanks glasser!
Merge branch 'bp-improvements' into devel
Update History.md for bp-improvements
Fix a typo in the API doc
Pass through the return value for update and remove on validated operations.

Fixes #1759.
Change many "maps from stringified ID" to _IdMap

This greatly reduces the number of places in the code where "stringified
IDs" are passed around.

Specifically, changed these maps into _IdMaps:

 - minimongo
   - the main LocalCollection docs map
   - LocalCollection._savedOriginals
   - unordered query results, in several places:
     - query.results
     - query.results_snapshot
     - return value from _getRawObjects
     - as passed to _diffQueryChanges
 - livedata
   - Connection._serverDocuments[collection]
 - mongo-livedata
   - SynchronousCursor._visitedIds
   - return value from SynchronousCursor.getRawObjects
   - PollingObserveDriver._results (when unordered)
Tests for "can selector become true by modifier" for simple $-operators
Fix wrong tests, separate "complex" tests to a separate scope.
Now Matcher.canBecomeTrueByModifier deals with simple $-operators with scalars:

- $gt, $gte, $lt, $lte
- $ne
- $nin, $in
More tests
Fix the way $in analysis worked
Catch if modifier surely modifies object when scalar expected
Update the comment in tests section
Fallback to "YES" in a case of noticeable floating point numbers underflow
Polish canBecomeTrueByModifier operators optimization

- Fix the pruning `expectedScalarIsObject`
- Limit $gt,$lt,... to numbers only (since there needs to be more logic to support dates and strings later)
- Add comments on dubious parts
Merge branch 'oplog-selector-modifier-operators' into devel

Brings optimizations to the oplog-tailing:
- analyze modifications coming from oplog and skip uneccessary fetches for certain $-operators
  + ranges of numbers { $gt: 5, $lt: 33 }
  + inequlities { $not: 5 } or { $nin: [ 1, 3, 4 ] } for scalars
  + equalities { $in: [ 2, 4, 6 ] } for scalars
Make default accounts-ui styling simpler/flatter
Refactor matchingDocument into separate method on Matcher's prototype, cache it.