Improve load/ save palette config

[kanurag94]

From #194 loading and saving of palette was introduced.

• Users can now open the palette config file .gpl with GIMP/ or can manually edit it.
• Options are now moved to Fractal -> Palette -> as Load Palette Config and Save Palette Config

[kanurag94]

Generated gpl file

GIMP Palette
Name: XaoS_Palette
Columns: 16
#
 10   2  15	 color_0
139 104 129	 color_1
 18  17  33	 color_2
189 178   3	 color_3
 19  33  10	 color_4
 95 172 117	 color_5
  3  22   3	 color_6
241 214  87	 color_7
 20  24   3	 color_8
243 176  41	 color_9
 22  24  28	 color_10
229 186 107	 color_11
 18  33   4	 color_12
 71 116 157	 color_13
 21  10  32	 color_14
153  94  63	 color_15
  7  24  21	 color_16
 91 248 209	 color_17
 12   7  29	 color_18
 13 194 211	 color_19
  3  21  31	 color_20
 47  60 197	 color_21
 20  30  34	 color_22
 65 230  39	 color_23
  3  16  14	 color_24
195  64 121	 color_25
 18  10  12	 color_26
 53 202  59	 color_27
  8   3  12	 color_28
 23   4 237	 color_29
  1   7  14	 color_30

[kovzol]

Nice improvement.
I think we should save the palette information also in the .xpf file (and also in the .png, of course), if there is a custom palette used. Otherwise the default palette will be shown which is not expected.

[kanurag94]

At this point I am not sure, if checking for default palette or not is easy. The xpf is parsed as a command parameter file, it'd be difficult to pass an array of colors or we can figure something out maybe. I have created issue #196 to track this.