Add argument validity checks to all commands

[shawn-nyk]

All "adev" commands now check for the presence of all necessary arguments before the rest of their parse methods are executed. This ensures that the appropriate error messages are thrown if any necessary arguments are missing.

[codecov-io]

Codecov Report

Merging #197 into master will decrease coverage by 0.04%.
The diff coverage is 33.33%.

@@             Coverage Diff              @@
##             master     #197      +/-   ##
============================================
- Coverage     45.28%   45.24%   -0.05%     
- Complexity      704      705       +1     
============================================
  Files           183      183              
  Lines          3363     3373      +10     
  Branches        393      396       +3     
============================================
+ Hits           1523     1526       +3     
- Misses         1750     1757       +7     
  Partials         90       90              

Impacted Files	Coverage Δ	Complexity Δ
...main/java/seedu/address/commons/core/Messages.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
.../logic/parser/add/AddApplicationCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ress/logic/parser/add/AddCompanyCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...s/logic/parser/add/AddInternshipCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ress/logic/parser/add/AddProfileCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...c/parser/delete/DeleteInternshipCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ss/logic/parser/edit/EditCompanyCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ss/logic/parser/edit/EditProfileCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...logic/parser/edit/EditInternshipCommandParser.java	39.28% <50.00%> (+2.24%)	3.00 <1.00> (ø)
...edu/address/logic/parser/add/AddCommandParser.java	100.00% <100.00%> (ø)	3.00 <0.00> (ø)
... and 2 more

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[orzymandias]

LGTM