Add a 'warning' to functions that are not standard Q methodology practice

[aiorazabala]

A message like this? (what do you think @maxheld83 )

"Warning: these functions are part of the 'qmethod' package, but they are not standard use in Q methodology studies, so make sure you understand what they do and/ or ask the authors."

At two points for each function:

• When running the function, add a line at the beginning with warning(...)
• In documentation

Add it to, e.g., the bootstrap functions:

• [x] qbstep()
• [x] qfsi()
• [x] qindtest()
• [x] qmb.plot()
• [x] qmb.summary()
• [x] qmboots()
• [x] qpcrustes()

Other of your new functions @maxheld83 ?

[aiorazabala]

Done