More flexible and simplified folder setup

[stojy]

As observed in #52, there are some folders assumptions that need to be cleaned up for a PinballY installation that doesn't use the PinballX folder setup.

Unlike PinballX, PinballY doesn't create it's media and database folders until they're needed. For example, the 'Media\Instruction Cards' folder isn't created until an instruction card is added to a table.

It's a very efficient design, but it causes a few related issues..

1. Day zero setup - it's not possible to run Scanner or Rebuilder until the folders are created.
2. Day n+1 setup - if certain features (e.g. instruction cards) are never used, then the folder won't be created.

The workaround is to create these folders manually (an empty directory is fine). The image below shows the required folders in purple.

Proposal..

1. Simplify folder setup. Since the PinballX and PinballY folder structure is nearly identical, only require the top level folder to be specified. For example, "c:\PinballY\Media" and then automatically calculate the other folders.
2. Cater for missing media sub-folders. Instead of disabling the entire Scanner/Rebuilder feature, just disable the relevant feature for the missing folder.

[stojy]

Implemented proposal 2 to cater for missing sub-folders by making the majority of them optional. Only the following folders are mandatory..

• tables
• frontend database