Improve semantics with new functions

New function has been introduced to perform specific mount actions,
previously performed with a combination of `mount` and the appropriate
`MountFlag`. Consequently the corresponding `MountFlag`'s have been
removed. Below is the list of new functions.

Remount a filesystem:

    remount

Bind a filesystem:

    bind
    rebind

Change propagation flags:

    makeShared
    makeRShared
    makeSlave
    makeRSlave
    makePrivate
    makeRPrivate
    makeUnbindable
    makeRUnbindable

Move a filesystem to a different mount point:

    move

Signed-off-by: Nicola Squartini <tensor5@gmail.com>
Update documentation

Signed-off-by: Nicola Squartini <tensor5@gmail.com>
New function: rBind

Signed-off-by: Nicola Squartini <tensor5@gmail.com>
mount: pass NULL when DriverData is empty

Signed-off-by: Nicola Squartini <tensor5@gmail.com>
Add .gitignore

Signed-off-by: Nicola Squartini <tensor5@gmail.com>
Update CHANGELOG.md

Signed-off-by: Nicola Squartini <tensor5@gmail.com>