open file, remember path

[szabgab]

Currently when we try to open a file padre automatically opens the directory where the current file is or the "My Documents".

This is not always the best strategy. Some users would like to have
a few directories remembered (or manually set) so they can navigate there easily.

Some will want only one but to be that the default.

Others (mostly unix/linux users) might prefer the default to be the "current working directory"

Once we have project support users might want to open file in a certain project.

[wwe]

retested with 0.82, Padre still opens a directory where the last opened file comes from or 'My Documents' by default