Changes for 2.0 (beta 4)

[sroebert]

This pull request contains more changes to more closely match Vapor MySQL. This will also be needed to perform further updates to PostgreSQL Driver.

Changes:

• Moved all methods from Database to Connection, leaving Database to be a simple class containing all the information to connect to a database.
• Updated PostgreSQLError and replaced all uses of DatabaseError with it.
• Created method for performing multiple queries in one transaction, using a specific isolation level.
• Added option to the listen function to stop listening.
• Prevented the listen function from crashing with a fatal error. Now an error is returned instead.
• Refactored all binding code into a similar structure as Vapor MySQL.
• Implemented handling of Date, instead of parsing the date into a string.
• Added unit tests for the new date type parsing.

[codecov-io]

Codecov Report

Merging #40 into master will decrease coverage by 10.07%. The diff coverage is 74.84%.

@@             Coverage Diff             @@
##           master      #40       +/-   ##
===========================================
- Coverage   90.05%   79.98%   -10.08%     
===========================================
  Files          17       10        -7     
  Lines        1970     1004      -966     
===========================================
- Hits         1774      803      -971     
- Misses        196      201        +5

Impacted Files	Coverage Δ
Sources/PostgreSQL/Database.swift	100% <100%> (+15.38%)	:arrow_up:
Sources/PostgreSQL/Bind/BinaryUtils.swift	98.1% <100%> (ø)
Sources/PostgreSQL/ConnectionInfo.swift	100% <100%> (+33.33%)	:arrow_up:
Sources/PostgreSQL/Bind/FieldType.swift	25.24% <25.24%> (ø)
Sources/PostgreSQL/Error.swift	17.5% <37.5%> (+12.23%)	:arrow_up:
Sources/PostgreSQL/Result.swift	65.62% <58.75%> (-26.05%)	:arrow_down:
Sources/PostgreSQL/Bind/Bind.swift	77.24% <77.24%> (ø)
Sources/PostgreSQL/Bind/Bind+Node.swift	94.79% <94.79%> (ø)
Sources/PostgreSQL/Connection.swift	95.89% <96.55%> (+11.42%)	:arrow_up:
Tests/PostgreSQLTests/MiscTests.swift
... and 3 more

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[Prince2k3]

I approve!