Add option to install language dictionaries

[damon-myers]

@RocketChat/DesktopApp

Closes #535

This PR adds an option to the Spellchecker menu to install a new language dictionary. It works by copying the dictionary to the app's dictionary directory and adding it to the list of available dictionaries.

[CLAassistant]

All committers have signed the CLA.

[gdelavald]

@damon-myers Hey! This is awesome, thanks for you contribution.
We'll review the PR and add comments if there are any changes needed.

[alexbrazier]

When testing this it seems to have enabled all dictionaries for me. I think it is caused by the change you made here.

[damon-myers]

@alexbrazier Thanks for catching that!

I corrected the dictionary issue you mentioned, and also tested the changes on Windows. I had only tested them on Linux beforehand, so I also made it so that the install menu option is only shown if you are not using system language dictionaries. (In that case you'd simply install the language via your operating system.)

[gdelavald]

Hey @damon-myers giving this branch a try, can you provide the dictionary you used to test this? Just checking if we can add this to the current release or if it's going to be postponed into the next version.
Thanks.

[damon-myers]

@gdelavald Sure thing, I used the dictionary .dic and .aff from here: https://cgit.freedesktop.org/libreoffice/dictionaries/plain/cs_CZ

I used Google to get some Czech text and it seemed to correct that correctly.

[ghost]

any news? it would be a huge improvment

[gdelavald]

@damon-myers Sorry for the delay on this, we have had some issues testing this branch, on osx and ubuntu we had some exceptions thrown when starting the app.
Could you check the functions that read from directories, since they seem to be causing errors in some cases?

[ghost]

@gdelavald anything new? do you have any logs with errors?

[damon-myers]

@monspid, Holy crap! Sorry! I got busy and didn't notice there were issues with this. I can take a look at the crashes this weekend and try to get the branch up to date.

[ghost]

It's a great NEWS :-) It would be a huge improvement

[damon-myers]

I rebased the branch against develop and made sure everything still works.

@gdelavald, I'm not able to reproduce the issue on Linux Ubuntu 17.10 or Windows (Windows uses system dictionaries, so this code isn't really used there.) Do you have any more information on the exceptions being thrown?

[ThomasVuillaume]

Can't wait to see that coming in, I had to copy over es_ES my fr_FR for now

[gabrielloberg]

We would love to have this functionality.

done

[engelgabriel]

@damon-myers can you please resolve the conflicts so I can merge this?

[damon-myers]

@engelgabriel, of course! On it!

[NatoBoram]

It's been a while since I tried to use different languages in Rocket Chat. There's this PR from one year ago that could fix that but wasn't merged, and this issue from two years ago.