Bug fixes and edit GUI

[tiuweehan]

Fix #156
Fix #161
Fix #168
Fix #169
Fix #172
Fix #190
Fix #193
Fix #196

Make ProblemDetails and PlanDetails editable and deletable
Update UG and DG

[coveralls]

Pull Request Test Coverage Report for Build 427

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 360 unchanged lines in 17 files lost coverage.
• Overall coverage decreased (-6.1%) to 48.103%

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Files with Coverage Reduction	New Missed Lines	%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/logic/commands/ClearCommand.java	1	0.0%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/ui/details/DetailsTabPane.java	3	0.0%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/ui/details/DetailsTab.java	7	0.0%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/model/ModelManager.java	8	79.39%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/ui/PlanListPanel.java	10	0.0%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/ui/ProblemListPanel.java	12	0.0%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/logic/LogicManager.java	14	58.82%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/model/plan/PlanList.java	15	75.64%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/ui/ProblemCard.java	16	0.0%
file:/home/travis/build/AY1920S1-CS2103T-W11-1/main/src/main/java/seedu/algobase/ui/display/DisplayTabPane.java	17	0.0%

Totals
Change from base Build 423:	-6.1%
Covered Lines:	2523
Relevant Lines:	5245

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💛 - Coveralls