added eager datatype checker for first 1000 rows

* I  do like  the change from VARCHAR to STRING. For the sake of separating concerns I would  do that in a separate PR though. - changed STRING back to VARCHAR
* And potentially have the 1000 constant in here incapsulated - Added EAGER_READ to ExcelConfiguration including boolean validateColumnTypes

* I  do like  the change from VARCHAR to STRING. For the sake of separating concerns I would  do that in a separate PR though. - changed STRING back to VARCHAR
* And potentially have the 1000 constant in here incapsulated - Added EAGER_READ to ExcelConfiguration including boolean validateColumnTypes

corrected a few tests cause these where breaking on the datatypes

switching devices

switching devices and apearantly autosave was off -_-

…om/SociopathicPixel/metamodel into dev/add-datatypes-to-excel-columns

# Conflicts:
#	excel/src/test/java/org/apache/metamodel/excel/ExcelDataContextTest.java

coudn't find any finals

…be better coded