### in qepcad, string formula does not work with the 'any-point' solution type

This is a bug report, please point me to another place, if there is a better one for bug reports.

`qepcad`

command allows for string formula input in the QEPCAD native format, but if in this case the `solution`

argument equals `any-point`

, the command fails with the error `Attempting to quantify variable which does not occur in formula`

```
# the following works, the formula is constructed with the qepcad_formula builder
var('a')
print(qepcad(qepcad_formula.implies(a > 0, a > 1)))
print(qepcad(qepcad_formula.implies(a > 0, a > 1), solution='any-point'))
# the following line works, solution is not 'any-point'
print(qepcad("[a > 0 ==> a > 1]", vars='a'))
# the next line does not work
print(qepcad("[a > 0 ==> a > 1]", vars='a', solution='any-point'))
```

The reason for the error is obvious from the source code. If solution is 'any-point', the formula is passed to the Qepcad initializer, that interprets the string as a variable name, but not as a formula.