Re-use existing connections

Check for existing connections to the vCenter server and re-use if they
exist. Saves duplicate connections and results.
Separate HTML template from code

Separated all HTML code from the vCheck.ps1 script to allow creation of
Style templates, migrated existing HTML code into a Default style.
Delete Header.jpg

Moved to /Styles/Default/Header.jpg
Added $Style setting to GlobalVariables
Changed to use Style folder structure
Add $Style=Default to GlobalVariables
Fixed style selection

Fixed style selection bug

Added "CleanGreen" example style
Merge pull request #49 from sammcgeown/master

Split HTML and CSS to a "Style" file
Performance improvement

Re-written using Get-VirtualSwitch and Get-VDPort - improved run time
from 120s to 12s on a 7 host vCenter.

Added settings variables to set a desired state for AllowPromiscuous,
ForgedTransmit and MacChanges.
Merge pull request #50 from sammcgeown/master

98 vSwitch Security Plugin - Performance improvement
Sort Plugin Time To Run Descending
Performance Improvements

Used the -IntervalMins parameter rather than the -Start and -Finish
parameters, this reduces the runtime by approx 60%. Testing showed each
Get-Stat call reduced from 5 seconds to 2 seconds, overall runtime for
48 VMs was reduced from an average of 333 seconds to 134 seconds.
Merge pull request #51 from sammcgeown/master

33 - CPU Usage plugin performance improvements