Add support for hardcoded, unmodifable portions of patten

[MarcinOrlowski]

Would be great if I could define some portions of pattern unalterable for user. For example I'd like user to enter his mobile phone number but I'd also like to restrict the country, i.e. +48 for Poland. For now I need to move +48 out of the pattern, to separate TextView, but if I'd just do i.e.

 [+48] 999 9999999

and the text in [] would be shown but be unalterable/non-erasable by user, it'd be great. When user finishes I'd like get it all back, incl. +48 part.

[ibrahimyilmaz7]

+1

Can't figure "9 (999) 999 99 99" pattern too.