Fix error message

Updated storage handling

Let the user run termux-setup-storage, which will ensure that storage
permission has been granted and setup $HOME/storage/ folder with
symlinks to storage folders.

Setup $HOME/storage symlink for external symlink

At startup Termux now checks if there is external storage available,
and creates a private area on the external storage if one exists as
well as creating a symlink to the private are at $HOME/storage.

Reformat code

Show bold text in bright colors

Fixes 17. Could be made an option in the future if necessary.

Bump version to 0.19

Add a file picker to pick files from $HOME

This allows e.g. files from the $HOME folder to be attached to emails
or uploaded when in other apps.

Also bump version to 0.18.

Bump version to 0.17

Also remove the version attributes from AndroidManifest.xml since
they are generated by the gradle build.