Code style changes

Make it more readable
Updated DESCRIPTION

- Added package details
- Added License
- Cleanup imports
Start of code refactoring

Basing on RSQLite
Added new file
Remove imports for assertthat
Create SQLServerDriver class; misc

Also updated package documentation
Refactor driver code
Implemented dbUnloadDriver()

Also added more docs on using integrated security with SQL Server
driver.
Starting connection implementation
Bit more package level doc
Updated DESCRIPTION & NAMESPACE
Using jTDS SQLServer driver (#2)

- SQLServer() calling jTDS driver and not MS driver
- URL build now uses jTDS conventions which also drops the need for
building property.
- Also added a few S4 methods for this driver: dbListConnections and
dbGetInfo
Updated doc & roxygenised

Also:

- Removed unnecesary argument to SQLServer()
- Updated function argument name in dbGetInfo to generic's name
Updated package doc & roxyenised
Add SQLServerResult class & imports

- rJava moved from Imports to Depends
- Added SQLServerResult class
DBIConnect methods

- Added code for DBIConnect methods. Most piggy back of JDBCConnect
class methods
- Updated docs
Corrected class returned by dbConnect
Minor code style change