Monitor data directory on portable mode

[sgourdas]

This simplifies the creation of a portable USB by automatically monitoring the data directory in portable mode. This way we allow the user to just place needed .zim files in the data folder and the app will handle the rest.

• Adds also immutability to the monitor and download paths through settings on portable mode

Fixes #461

[kelson42]

LGTM from user perspective
@veloman-yunkan ready for the code review

[kelson42]

@sgourdas Might that be that settings UI about monitoring directory should be greyed, as any value will be overriden at start by the code?

[sgourdas]

@kelson42 sure, but should that be the case only for the monitor directory?

[kelson42]

@sgourdas Yes, I think so... because whatever this settings is set it will be reseted at start right? For the other settings, the user can change them and they will be kept!

[sgourdas]

@sgourdas Yes, I think so... because whatever this settings is set it will be reseted at start right? For the other settings, the user can change them and they will be kept!

@kelson42 no, that is not the case at the moment per this commit. Monitor and download directory are currently hardcoded to the data directory on every portable start.

What would the desired behavior be?

[kelson42]

@sgourdas Yes, I think so... because whatever this settings is set it will be reseted at start right? For the other settings, the user can change them and they will be kept!

@kelson42 no, that is not the case at the moment per this commit. Monitor and download directory are currently hardcoded to the data directory on every portable start.

What would the desired behavior be?

Then I guess both should be greyed in portable mode (only).

[sgourdas]

@sgourdas Yes, I think so... because whatever this settings is set it will be reseted at start right? For the other settings, the user can change them and they will be kept!

@kelson42 no, that is not the case at the moment per this commit. Monitor and download directory are currently hardcoded to the data directory on every portable start.
What would the desired behavior be?

Then I guess both should be greyed in portable mode (only).

@kelson42 I added immutability on these two in portable mode. It includes grayed out text, disabled buttons and tooltip to explain the disabling.

[kelson42]

@sgourdas LGTM, please rebase so we can proceed with merging.