addAutoReplace - limit all inputs to strings only

:Release Notes:
"addAutoReplace" accept only string as input

:Detailed Notes:
"addAutoReplace" accept only string as input

:Testing Performed:
Was tested on Starfish build 236

:QA Notes:
correct request:
luna-send -n 1 -f palm://com.palm.smartKey/addAutoReplace '{ "shortcut":"OuluU", "substitution": "Oulu Univeristy"}'

wrong request:
luna-send -n 1 -f palm://com.palm.smartKey/addAutoReplace '{ "shortcut":"OuluU@", "substitution": "Oulu Univeristy"}'
or
luna-send -n 1 -f palm://com.palm.smartKey/addAutoReplace '{ "shortcut":"OuluU", "substitution": "Oulu123-Univeristy"}'

:Issues Addressed:
[GF-10659] com.palm.smartKey:addAutoReplace - accepting all inputs

Open-webOS-DCO-1.0-Signed-off-by: Igor Kuksyuk <ikuksyuk@luxoft.com>

Change-Id: Id920f1ce2dab095fdf9c5415d68d43b2a4bb9fea
Reviewed-on: https://g2g.palm.com/2917
Reviewed-by: Build Verification
Reviewed-by: Igor Kuksyuk <ikuksyuk@luxoft.com>
Tested-by: Igor Kuksyuk <ikuksyuk@luxoft.com>
Reviewed-by: Roger Stringer <roger.stringer@lge.com>