Fix Installation Blocks w/ Overridden Controller

Fix installation of blocks with overridden controller but not an
overridden db.xml file.

This caused an upgrade error from upgrading 5.6.0.2 to 5.6.1

- Add additional parameter to `BlockType::doInstallBlockType()` to account
for `db.xml` location.
- Add check for `FILENAME_BLOCK_DB` as well as
  `FILENAME_BLOCK_CONTROLLER` as these could be different directories.
Merge pull request #964 from mkly/bugfix_install_block_with_override_controller_bttable_dbxml

Fix Installation Blocks w/ Overridden Controller