Make shift-delete/shift-backspace behavior match non-shift behavior

Closes #1839
Don't bind shift-delete, only shift-backspace

See 6c62022d44b3660ad75204943393bd6ea78bb228
[hardwrap addon] Add
[hardwrap addon] Fix bugginess when wrapping multiple paragraphs
[real-world uses] Add Codio
[real-world uses] Fix misspelled url
[sql_mode] added keywords

* added keywords from mysql & mariadb recent versions
[themes] Move error style to bottom to give it precedence
[xml mode] Leave old style intact when adding error style

Fixes a problem with matchtags getting confused.

Closes #1841
[xml mode] Leave tag tokenizer when encountering '<'

Issue #1841
adding gherkin mode
[gherkin mode] Remove double mime definition
[css] Fix indentation issue in SCSS mode with mixin variables (closes #1846).

Also improve handling of parentheses and curly braces.
[css] Add tests for indentation
[css mode] Clean up whitespace

Kill all tabs.

Issue #1851
[manual] Fix incorrect mention of class used by matchtag addon
[real-world uses] Add PrinBit, complete.ly
[real-world uses] Add webappfind
[closetag addon] Fix false positive close situation

Closes #1844
[eiffel mode] Add