Changed functionaility of Save Button

[qhen143]

• Modified 'Save' button to 'Change Save Directory'.
• Remove 'File Location Saved To' in favour of placeholder.
• Clicking this button will now allow the user to select a directory to clone the repository to, without calling any clone command immediately after.
• The text input relating to the save directory will also be updated whenever changed.

Resolves #118 . Resolves #1 and #13 .

To test #13:

1. Enter a remote URL.
2. Clear the text input for directories.
3. Click the 'clone' button'. Expected: Folder select should open up.

To test new 'select directory' functionality (#118 ) and cloning with URL (#1) :

1. Enter a remote URL.
2. Click the 'select directory' button.
3. Select a directory.
4. Click the 'clone' button'. Expected:

• The text input for directory should show the relative path if path is within the app directory else full path is shown.
• Repository from remote URL should be cloned in that path.

EDIT 9/4/2019: Tests are outdated with the modifications from #136 . Tests now related to #143 .