Initial changes to attempt to develop a locking mechanism for db files
during copy
Removed:

- Initial tests from AMDatabase relating to locking and unlocking using
PRAGMA (was unstable)
- Registering of AMDirectorySynchronizationAction in AMAppController

Added:
- More documentation to class AMDirectorySynchronizationAction
- AMDatamanAppController::startupBackupDataDirectory() ~ function to run
modal dialog if AM is started with remote directory in ini file

Altered:
- AMDirectorySynchronizerDialog::start() now runs exec instead of show,
in order to ensure that the AMDatamanAppController startup is blocked
till the dialog is complete.
- AMDatamanAppController::startup() now includes a call to
startBackupDataDirectory