Sqlite::truncate(): Verify `sqlite_sequence` exists before _execute()

`sqlite_sequence` is a dynamic table that's only available when a table in
the database use an auto increment field.  For some cases, eg: databases that
exclusively use uuid for primary keys, this table won't exist and
truncate() call will fail with:

  Error: SQLSTATE[HY000]: General error: 1 no such table: sqlite_sequence
Reduce variable use/duplicate code.
Added/removed newlines to make the code more readable.
Merge pull request #1617 from davidsteinsland/master

Fixed race conditions for FileEngine.

Using file_exists() and unlink() together does not ensure atomic results.
Add coding standards ignore comments to FileEngine

We normally disallow error supression but it is the only way to
atomically delete files.
Remove last yoda conditions as per coding standards guidelines.
Merge pull request #1618 from dereuromark/master-cs

Remove last yoda conditions as per coding standards guidelines.
JsonView should return null if no data is set, regardless of the type of '_serialize'.
It should also honor true/false/0/'' values.
Merge pull request #1613 from bar/json-view

JsonView should return null if no data is set, regardless of the type of '_serialize'.
Fixed handling null values in Sqlserver->value

The value function quoted a null value as N'' instead of NULL.
As a result is produced queries like [name] IS N'' instead of [name] IS NULL which resulted in an SQL error.
Quoting test for null value and string column
Merge pull request #1620 from ovidiupruteanu/patch-1

Fixed handling null values in Sqlserver->value().

Fixes #3768
Fix whitespace.
Add test for insertMulti with id in the last spot.

Both tests work, so there are no changes to the implementation.

Closes #4048
Fix CS.
Update afterSave() callback signature to be PHP5.4+ compliant.
Fix clearing groups with FileCache and no prefix.

If you used FileCache + groups + an empty prefix cached files would not
be cleared as strpos() would fail.
Merge pull request #1622 from bar/php54-afterSave

Update Model/Behavior afterSave() callback signature to be PHP5.4+ compliant.
Update afterFind() callback signature to be PHP5.4+ compliant.
Fixed setting of order in Paginator options when using model's order. Refs f680c76, #3902