(1) e_config.c/e_comp_wl.c: add code for making repeat values configurable

(1) e_config.c/e_comp_wl.c: add code for making repeat values configurable
(2) e.src(s): add keyboard.repeat_delay, keyboard.repeat_rate into e.src files

Summary:
As of now, the default values of repeat delay/rate are being set in e_comp_wl.c.
Those values need to be configurable and will be used in e_comp_wl_init().
The limit of each of the values is defined from -1 to 1000. (maximum 1s).
If one of the two is negative, it means default repeat delay/rate are going to be used.
(e.g. delay:400, rate:25)

Test Plan:
N/A

Signed-off-by: Sung-Jin Park <input.hacker@gmail.com>
Reviewers: raster, stefan_schmidt, gwanglim, devilhorns, zmike

Subscribers: Jeon, ohduna, cedric

Differential Revision: https://phab.enlightenment.org/D3364