Add skeletal code for add and delete parser

[orzymandias]

• Lay out skeletal code for Add and Delete parsers to avoid conflicting commits.
• Implement add and delete abstract classes for different item commands.
  closes Skeletal code for Add and Delete Parsers #119

[seanjyjy]

Overall looks great, just some nits to fix.

Just a side question as to would it be confusing as AddCommandParserWrapper is essentially Similiar to DeleteCommandParser, however, they have different naming syntax.
Is this implementation temporary in order to allow ab3 to function properly?

[seanjyjy]

If most to all parser requires these static final int variables, we could shift it to avoid duplicates. However, I am not sure if it is apt to shift it to an interface. Can consider having a Util class for it.

[orzymandias]

Sounds good! I was thinking of doing so after the other parsers are done since for example the EditParser for the InternshipCommand may want to abstract 3 items (comindex, index ,prefixes)? So it depends on implementation of the parsers first then after which we deal with abstraction for common vars.

[orzymandias]

Overall looks great, just some nits to fix.

Just a side question as to would it be confusing as AddCommandParserWrapper is essentially Similiar to DeleteCommandParser, however, they have different naming syntax.
Is this implementation temporary in order to allow ab3 to function properly?

For AddCommandParserWrapper each item has its own set of parsing rules which may require their own individual parsers so the AddCommandParserWrapper is only responsible for funneling the appropriate item prefix to its add parser. The thing about delete command parser is that there is lesser parsing involved except for extracting out the index to be deleted. With the exception of internship which has an additional index required, all the other commands just need the index extracted to be passed to their delete commands. So I am not sure there is a need a wrapper in that case.

As for consistency I think once AddCommandParser can be safely removed, we can rename AddCommandParserWrapper to AddCommandParser.

[seanjyjy]

LGTM good job.