Fix double line issue

[onebuck-code]

Tested on 3 types of printer printing english and chinese.
No more double line spacing after removed the LINE_SPACE_88 and LINE_SPACE_68

[husseinm]

@leesiongchan Can we please merge this?

This is a simple fix for the library that gives the user total control over their receipts.

Without this you lose the ability to double space without extra lines - this kills the library for me (much so that I have to fork to fix it and maintain accordingly)

At the very least to avoid backward compatibility can we add new symbols? My suggestion would be for the following:

• {H1NWS} = H1 No White-Space
• {H2NWS} = H2 No White-Space
• {H3NWS} = H3 No White-Space
• {NL} = New Line