Rename Application and Execution Context classes

The current pre-packaged execution context and application classes are not really named in a way that makes thie functionality clear.

The following is a proposed rename of the pre-packaged classes:

Current Class	New Class
`SimpleContext`	`TemplateCtx`
`AppContext`
`SimpleAppContext`	`ClientSessCtx`
`SessionAppContext`	`ServerSessCtx`
`SessionFileAppContext`	`FileSessCtx`
`Application`
`SimpleApp`	`ClientSessPageObjApp`
`SimpleSessionApp`	`ServerSessPageObjApp`
`SimpleSessionFileApp`	`FileSessPageObjApp`
`ModularApp`	`ClientSessPageModApp`
`ModularSessionApp`	`ServerSessPageModApp`
`ModularSessionFileApp`	`FileSessPageModApp`
`RandomModularApp`	`ClientSessByURLPageModApp`
`RandomModularSessionApp`	`ServerSessByURLPageModApp`
`RandomModularSessionFileApp`	`FileSessByURLPageModApp`