TileDimensionCalculator = function(oTileContainer) {
		this._oDim = null;
		this._oTileContainer = oTileContainer;
	}
Calculates a common Tile dimension (width and height) applied for all the Tiles.
Function {@link getLastCalculatedDimension} does not do the calculation.
The caller must explicitly call the {@link calc} function before it, or when he/she wants up-to-date dimension.
@param {sap.m.TileContainer} oTileContainer The sap.m.TileContainer for which the dimensions will be calculated
@private