Add options to store global default and per-workbook default export folder locations

[bskinn]

Can just add a couple of buttons to the form and store (a) the per-workbook default folder in that workbook, and (b) the global default folder in the .xlam.

Should implement a ~hidden helper function to easily clear the default folder from the .xlam.

Could also implement storage of all of the parameters on the form.

[bskinn]

Form is getting complex enough that it's annoying to have to reconfigure everything every time.

[bskinn]

Storage of the save-to folder path will require addition of a validity check on that path. If the path isn't to an existing folder (maybe even check if it's writeable?), then disable export and change the font color to red.

[bskinn]

Probably implement ClassModule to hold settings info, translate to/from settings string. Probably makes the most sense to house the core defaults in this class, which are spit out if there's no settings Property on the .xlam or the active workbook, or if parsing of the options string fails.

Nonprintable character in settings string as separator?

[bskinn]

Add option to save multiple settings configurations? New modal dialog for settings save/load. Would want to stack all settings into a single document property, or else the number of properties would rapidly get out of hand.

OTOH, there's a character limit for document properties, but apparently no functional limit to the number of document properties that can be created.

Looks like the better way to go is to use Workbook.CustomXMLParts (see here and here, which does not have a size limit and which is intrinsically a structured datatype!

Maybe there's an XML parsing/writing library already available in the builtin References, too....