Fix/script sync delete options

[aagm]

Changes:

• Add deletion of assets in sync as optional.
• Modify the way the sync file is generated to avoid a weird issue with the metadata. Adding a diff capabilities between the old file and the new one with a compound version of it.

[tamaramegan]

I am getting strange behaviours. From staging to prod the widgets are not copied, but if done from prod to staging the widgets are duplicated.
Also, it is nor clear the behaviour of overwrite, merge or keep oldfile. Some more explanations would be good in general about what to expect in each case.