Efl Canvas Text : Modify Style Property

Efl Canvas Text : Modify Style Property

Summary:
This patch defines the way style property will work at canvas_text object

1- Changing canvas_text style property using Font/Format/Style interfaces or with efl_canvas_text style property are the same.
     Example:

```
efl_text_font_set(tb, "Arial", 30);
//is same as
efl_canvas_text_style_set(tb, "font=Arial font_size=30");

//which means calling
char * font;
int size;
int font_size;
efl_text_font_get(tb, &font, &size);
// calling this after any of the top two functions will return same result
```

2- style_get_property
     Will return string that contains full details about all the current applied style at canvas_text  level.

3- style_set_property
     Will only override passed styles and leave everything else as it is

```
efl_canvas_text_style_set(tb, "font=Arial");  // overrider font name to Arial and leave everthing else
efl_canvas_text_style_set(tb, "font_size=30");  // overrider font size to 30 and leave everthing else (font name will stay arial)
```

Reviewers: ali.alzyod, woohyun, tasn, segfaultxavi, bu5hm4n, zmike

Reviewed By: woohyun

Subscribers: zmike, bu5hm4n, segfaultxavi, a.srour, cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D10607