Return the property value range in getInfoAtPos() api.
Fix several issues raised in #7149:
* When search scope is a single file, skip exclusion filter entirely
* If exclusions filter results in 0 files to search, show a message to that
effect and leave search bar open so user can adjust filter
* When editing a filter, show how many files are still included out of the
total number of files in the current search scope

Also cleans up FindInFiles to centralize the filtering code more, and
simplify _doSearchInOneFile() & its call sites.
simple unit test
Revert "Merge pull request #7392 from adobe/dangoor/revert-help"

This reverts commit 576da47c798bc446b8102184482f746e986416d8, reversing
changes made to 62aef708bd493c4a6637b42c9dd21a6bf7809a2e.
Changes the help menu to point people at the Troubleshooting wiki page and the new
Suggest a Feature page.
Changes requested in review
'enhanced' the test data
updated unit test data
Merge branch 'master' into rlim/range-in-css-info
update range unit tests
Code review: restyle filter editor file count and make UI element widths
cleaner. Fix some stale docs and other nits.
Merge branch 'master' into dangoor/help-menu-2
Reword Brackets Support
Fix bug #7402 (Focus not set to inline editor after creating new rule) - If
the client of the DropdownButton changes focus in respond to the "select"
event that closes it, leave focus in that new location. Only restore focus
to where it was before dropdown closed if no one has touched the focus while
closing.
Fix all CSS Context Info unit tests by adding range info.
Merge pull request #7419 from adobe/pflynn/fix-dropdown-focus-restore

Fix bug #7402 (Focus not set to inline editor after creating new rule)
Merge pull request #7400 from adobe/pflynn/exclusions-improvements

File exclusions usability improvements (bug #7149)
Merge pull request #7410 from adobe/dangoor/help-menu-2

Help menu changes, version 2
rtc: spelling errors
Handle ranges for empty property values and fix some more unit tests.
And also address two review feedbacks.