[FEATURE] Define Flux forms in TypoScript

Usage example:

```
plugin.tx_flux.providers.myProvider {
	tableName = tx_extname_domain_model_table
	fieldName = myfield
	templatePathAndFilename = path/to/Template.html
}
```

Another example:

```
plugin.tx_flux.providers.myProvider {
	tableName = tx_extname_domain_model_table
	fieldName = myfield
	form {
		fields {
			test {
				# the "type" here corresponds to the last part of the class name in the
				# FormComponent - fx "Input" or "Select" (note case). It can also be
				# a full class name of any third-party Component implementing the
				# proper interface.
				type = Input
				label = Demo field
			}
		}
		# and/or wrap "fields" in a "sheets" section with individual sheets:
		sheets {
			sheet1 {
				label = Sheet no. 1
				fields { ... }
			}
			sheet2 {
				label = Sheet no. 2
				fields { ... }
			}
		}
	}
}
```