Improve Import-TfsTeamProjectAvatar parameter handling

[igoravl]

• Add pipeline support to Project argument
• Add argument positioning support

[igoravl]

Missing pipeline support:

New-TfsTeamProject MyProject -Passthru | Import-TfsTeamProjectAvatar -Path "C:\foo\bar\MyProject.png"
# Import-TfsTeamProjectAvatar: The input object cannot be bound to any parameters for the command 
# either because the command does not take pipeline input or the input and its properties do not match 
# any of the parameters that take pipeline input.

Missing argument positioning support:

Import-TfsTeamProjectAvatar MyProject -Path "C:\foo\bar\MyProject.png"
# Import-TfsTeamProjectAvatar: A positional parameter cannot be found that accepts argument 'MyProject'.