Table and row-oriented input data

There is no direct way to construct a `Table` from a row-oriented list of values like:

    [('a', 1, 1.0), ('b', 2, 2.1)]

The documentation actually addresses [this issue][1], but it is buried at a level where users can easily miss it.  As explained in the "Python arrays versus `numpy` arrays as input" subsection, the flexible nature of the current column-oriented approach makes it basically impossible to determine from the data alone if it is row- or column-oriented.  Making a distinction between tuples and lists for the inner element will be error-prone for users who may not even understand there is a difference.

Proposal:

1. Put some notes to clarify in much more obvious places.
2. Consider adding a keyword to `Table` (e.g. `row_oriented` or something to that effect) which explicitly states that the input data is a list of rows.

[1]: http://astropy.readthedocs.org/en/latest/table/construct_table.html#numpy-homogeneous-array