spinner: add invalid input validity filter

spinner: add invalid input validity filter

Summary:
Do not allow invalid input in to spinner.
Invalid Input can be:
1. '-' should not be inserted anywhere but the starting position, and no more than one '-' can be inputted.
2.  No more than one '.' can be inserted.

Signed-off-by: Shilpa Singh <shilpa.singh@samsung.com>
@feature

Test Plan:
1. Launch elementary test
2. Run spinner demo
3. Enter invalid inputs like inserting more than one '.', '-' or insert '-' anywhere else part from 1st position.

Reviewers: raster, CHAN, subodh6129, cedric

Subscribers: govi, buds

Differential Revision: https://phab.enlightenment.org/D3664

Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>