Add information about the exclusion of financial firms

[christophscheuch]

Because we received a request, we need to add:

• Clarification in */wrds-crsp-and-compustat that industry format INDL excludes financial firms to some extent.
• Footnote (?) in */replicating-fama-and-french-factors that states that theoriginal Fama & French (1992) paper claims to exclude financial firms. To some extent this happens through using industry format "INDL". Neither the Fama & French (1994) paper, nor Ken French's website or the WRDS replication contains any indication that financial companies are excluded using additional filters such as industry codes.