added a button to create a new mirror entry

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
for editing an existing mirror's provider use the appropriate field in editMirror

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
revamp edit mirror and cancel mirror: one is to initiate editing of an existing mirror and the other cancels editing of new or existing mirrors

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
add creating of new mirrors to the frontend

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
updated icons in mirror edit to change color on hover

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>