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.
flushMethodCache not working if called before cacheMethod

When calling flushMethodCache it correctly empties self::$methodCache but if cacheMethod is called afterwards self::$methodCache gets populated with data from the Cache.
performance improvements in Model::_clearCache

- don't empty cache twice if pluralized name is identical to underscored
- refactors for fewer function calls
Refactors Model::_clearCache

- don't use mixed keys in $assoc array
- removes unnecessary strtolower on Inflector::underscore result
- return early
Test case for DboSource::flushMethodCache
Merge pull request #1687 from Schlaefer/model-cache-improvements

performance improvements in Model::_clearCache
Correct spelling mistake in class name.
fixes FileLog doesn't delete on rotation if count(files) is greater 'rotate'
fixes FileLog doesn't delete on rotation if `rotate` = 0
Correct method names and missing parent calls.
Changed url to URL where appropriate
Merge pull request #1709 from bcrowe/hotfix-url

Changed url to URL where appropriate
Merge pull request #1705 from Schlaefer/FileLog-RotateOlderLogs

fixes FileLog doesn't delete on rotation if count(files) is greater 'rotate'
Fix content view variable being stomped by send() parameter.

The content of send() should only be used if it is a non-empty value.

Fixes #4129
Replace deprecated methods.
Make equality checks more strict.
Merge pull request #1712 from dereuromark/master-deprecated

Replace deprecated methods.
Capitalize UUID acronym