change labels for pIC50, pEC50 etc. to IC50, EC50

FIX #200

ippisite/ippidb/forms.py

@@ -937,10 +937,20 @@ class CompoundActivityResultForm(ModelForm):
 
 class CompoundActivityResultBaseInlineNestedFormSet(BaseInlineNestedFormSet):
     __compound_names = []
+    # pIC50, pEC50, etc. activity types are labelled below as IC50, EC50, etc.
+    # specifically because the user enters them in these forms as the former
+    # value but they are converted to and stored in the latter.
+    __activity_types = [
+        ("pIC50", "IC50 (half maximal inhibitory concentration)"),
+        ("pEC50", "EC50 (half maximal effective concentration)"),
+        ("pKd", "Kd (dissociation constant)"),
+        ("pKi", "Ki (inhibition constant)"),
+    ]
 
     def add_fields(self, form, index):
         super().add_fields(form, index)
         form.fields["compound_name"].choices = self.__compound_names
+        form.fields["activity_type"].choices = self.__activity_types
 
     def set_modulation_type(self, modulation_type):
         for form in self.forms: