imgtool: make "align" command line parameter optional

[butok]

"Align" parameter should be optional:

• it has a default value.
• it is not used for non-swap update modes.

[mingulov]

Sorry could someone clarify how it was intended to work / where it works?

For me without 'align' option I receive an exception on 'align=int(align)':
TypeError: int() argument must be a string, a bytes-like object or a real number, not 'NoneType'

[butok]

Sorry could someone clarify how it was intended to work / where it works?

For me without 'align' option I receive an exception on 'align=int(align)': TypeError: int() argument must be a string, a bytes-like object or a real number, not 'NoneType'

Interesting, why we are using align=int(align).
All other integer parameters do not have such approach ( slot_size=slot_size, max_sectors=max_sectors, max_align=max_align etc.).
Guess, we should delete int(). May we?