Introduced concept of non-read-only properties

[Kittyfisto]

Reason for this MR

In preparation for #284

Now that log files can expose an arbitrary list of properties and Tailviewer can show these to the end-user, we want to allow the user to be able to change a select few. Which properties may changed is determined by its descriptor. Only a subset of all properties will ever be changeable by the user, and thus by default all properties are read-only. Only those properties which implement the non-read-only tag interface IPropertyDescriptor may be changed by end-users. All others remain read-only.

With this, we give an ILogFile implementation an amazing flexibility to interact with its users:

Plugins may ship their own properties, have them exposed to the user and the user will be able to change them back to which the plugin can react again.

List of changed types

• Renamed ILogFilePropertyDescriptor to IReadOnlyPropertyDescriptor
• Introduce IPropertyDescriptor for non-read-only properties
• Changed LogFileProperties.Encoding to be non-read-only
• Added IlogFile.SetProperty() method
• Renamed LogFileColumns class to Columns in context, the LogFile suffix was superfluous
• Renamed LogFileProperties class to Properties in context, the LogFile suffix was superfluous

Added plugins

Introduced the IPropertyPresenterPlugin which allows plugin authors to create their own custom IPropertyPresenters in case those created by Tailviewer by default are not their liking.

Any expected problems concerning backwards compatibility of existing plugins?

Yes

Any expected problems concerning backwards compatibility of existing user settings?

No

Does this break existing user workflows?

No

[Kittyfisto]

@BenKenobi85 You better like this new progress bar or else (:P):

[BenKenobi85]

It's so awesome!! :P